Fix threading on counts::apply when there are no rows/columns.

In such cases, it is possible for the number of threads to be zero, in which
case we should ask for an allocation of length 'num_threads - 1'.

CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 
 project(tatami_stats
-    VERSION 1.1.2
+    VERSION 1.1.3
     DESCRIPTION "Matrix statistics for tatami"
     LANGUAGES CXX)
 

include/tatami_stats/counts.hpp

@@ -89,11 +89,14 @@ void apply(bool row, const tatami::Matrix<Value_, Index_>* p, Output_* output, i
     } else {
         num_threads = subpar::sanitize_num_workers(num_threads, otherdim); // provides some protection against silly num_threads iputs.
         std::vector<Output_*> threaded_output_ptrs(num_threads, output);
-        std::vector<std::vector<Output_> > threaded_output(num_threads - 1);
-        for (int t = 1; t < num_threads; ++t) {
-            auto& curout = threaded_output[t - 1];
-            curout.resize(dim);
-            threaded_output_ptrs[t] = curout.data();
+        std::vector<std::vector<Output_> > threaded_output;
+        if (num_threads > 1) {
+            threaded_output.resize(num_threads - 1);
+            for (int t = 1; t < num_threads; ++t) {
+                auto& curout = threaded_output[t - 1];
+                curout.resize(dim);
+                threaded_output_ptrs[t] = curout.data();
+            }
         }
 
         if (p->sparse()) {

tests/src/counts.cpp

@@ -5,7 +5,7 @@
 #include "tatami_stats/counts.hpp"
 #include "tatami_test/tatami_test.hpp"
 
-TEST(ComputingDimCounts, RowNaNCounts) {
+TEST(ComputingDimCounts, RowNanCounts) {
     size_t NR = 99, NC = 152;
     auto dump = tatami_test::simulate_vector<double>(NR * NC, []{
         tatami_test::SimulateVectorOptions opt;
@@ -51,7 +51,7 @@ TEST(ComputingDimCounts, RowNaNCounts) {
     EXPECT_EQ(ref, tatami_stats::counts::nan::by_row(unsorted_column.get()));
 }
 
-TEST(ComputingDimCounts, ColumNaNCount) {
+TEST(ComputingDimCounts, ColumNanCounts) {
     size_t NR = 79, NC = 62;
     auto dump = tatami_test::simulate_vector<double>(NR * NC, []{
         tatami_test::SimulateVectorOptions opt;
@@ -138,7 +138,7 @@ TEST(ComputingDimCounts, RowZeroCounts) {
     EXPECT_EQ(ref, tatami_stats::counts::zero::by_row(unsorted_column.get()));
 }
 
-TEST(ComputingDimVariances, RowZeroCountsWithNan) {
+TEST(ComputingDimCounts, RowZeroCountsWithNan) {
     size_t NR = 52, NC = 83;
     auto dump = tatami_test::simulate_vector<double>(NR * NC, []{
         tatami_test::SimulateVectorOptions opt;
@@ -238,3 +238,36 @@ TEST(ComputingDimVariances, ColumnZeroCountsWithNan) {
     EXPECT_EQ(ref, tatami_stats::counts::zero::by_column(sparse_row.get()));
     EXPECT_EQ(ref, tatami_stats::counts::zero::by_column(sparse_column.get()));
 }
+
+TEST(ComputingDimCounts, EmptyCounts) {
+    size_t NR = 0, NC = 10;
+    auto dense_row = std::unique_ptr<tatami::NumericMatrix>(new tatami::DenseRowMatrix<double, int>(NR, NC, std::vector<double>()));
+    auto dense_column = tatami::convert_to_dense(dense_row.get(), false);
+    auto sparse_row = tatami::convert_to_compressed_sparse(dense_row.get(), true);
+    auto sparse_column = tatami::convert_to_compressed_sparse(dense_row.get(), false);
+
+    tatami_stats::counts::zero::Options nopt;
+    nopt.num_threads = 3;
+
+    std::vector<int> empty_c(NC);
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(dense_row.get()));
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(dense_column.get()));
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(sparse_row.get()));
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(sparse_column.get()));
+
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(dense_row.get(), nopt));
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(dense_column.get(), nopt));
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(sparse_row.get(), nopt));
+    EXPECT_EQ(empty_c, tatami_stats::counts::zero::by_column(sparse_column.get(), nopt));
+
+    std::vector<int> empty_r(NR);
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(dense_row.get()));
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(dense_column.get()));
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(sparse_row.get()));
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(sparse_column.get()));
+
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(dense_row.get(), nopt));
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(dense_column.get(), nopt));
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(sparse_row.get(), nopt));
+    EXPECT_EQ(empty_r, tatami_stats::counts::zero::by_row(sparse_column.get(), nopt));
+}